HTTP functions as a request-response protocol in the client-server computing model. In HTTP, a web browser acts as a client, while an application running on a computer hosting a web site functions as a server. The client submits a HTTP request for a HTTP page to the server. In response to the HTTP request, the server returns a HTTP response to the client. Normally, the HTTP response by the server fetches all the contents of the HTTP page and passes all the contents to the client. Therefore, duplicated/redundant data are transmitted via a network. To overcome this problem, AJAX (Asynchronous JavaScript and XML) is introduced to partly refresh web contents. AJAX is a group of interrelated web development techniques used on the client-side to create asynchronous web applications, and AJAX-based web applications are growing in popularity. In addition, there are technologies of delta transfer and diff transfer based on HTTP, such as Apache Subversion (SVN).